Abstract 19357: Direct Measurement of Thoracic Duct Pressure in Patients With Fontan Physiology

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Introduction: We have reported on anatomic and lymphatic flow abnormalities in patients with lymphatic complications of single ventricle physiology, such as chylothorax (CTX), plastic bronchitis (PB), and protein losing enteropathy (PLE). To date, little is known about lymphatic physiology in the setting of chronically-elevated central venous pressure or its role in the development of lymphatic complications.

Methods: This study is a single-center retrospective review of direct thoracic duct (TD) pressure measurements in 22 Fontan patients presenting for lymphatic interventions between April 2016 and April 2017.

Results: Of the 22 patients, 17 (77%) had PB, 5 had PB with concurrent PLE, and 5 (23%) had CTX alone. The median age at the time of lymphatic intervention was 6.6 years (IQR 4.0 - 9.8). Overall, the median value for TD mean pressure was 15 mmHg (range 9 - 29) and the median value for Fontan mean pressure was 15 mmHg (range 12 - 20). Individually, 6 patients (27%) had a lower TD pressure than their Fontan pressure (median difference -2 mmHg, IQR -1 to -4), 5 patients (23%) had a TD pressure equal to their Fontan pressure, and 11 patients (50%) had a higher TD pressure than their Fontan pressure (median difference +4 mmHg, IQR +1 to +10). The TD pressure waveforms were non-pulsatile at baseline and followed a similar respiratory pattern to the Fontan pressure waveforms. With acute TD outlet occlusion in 3 patients, the TD pressure increased significantly and became pulsatile, while the venous pressure waveform did not change.

Conclusions: Central lymphatic pressure is elevated in Fontan patients undergoing lymphatic interventions. In half of the 22 patients, the TD pressure was higher than the Fontan pressure. In these patients, lymphatic abnormalities may be the cause and/or consequence of this result and further exploration is needed. Additionally, with acute TD occlusion, the TD pressure increased significantly above the venous pressure and the TD pressure waveform became pulsatile, which may have implications on procedural and clinical outcomes when performing TD embolization. Finally, determining the lymphatic hemodynamics in Fontan patients without any clinically-apparent lymphatic abnormalities could help us better understand these findings.

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